Acoustic wave element having high acoustic velocity layer

ABSTRACT

An acoustic wave element is disclosed. The acoustic wave element can include a piezoelectric layer that includes aluminum nitride. The acoustic wave element can also include a diamond like carbon layer. the acoustic wave element can further include an interdigital transducer electrode that is positioned on the piezoelectric layer. The piezoelectric layer is positioned between the interdigital transducer electrode and the diamond like carbon layer. The acoustic wave element is configured to generate a Lamb wave having a wavelength of λ.

CROSS REFERENCE TO PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/907,023, filed Sep. 27, 2019 and titled“ACOUSTIC WAVE RESONATOR WITH SPINEL SUBSTRATE,” and U.S. ProvisionalPatent Application No. 62/907,021, filed Sep. 27, 2019 and titled “LAMBWAVE DELAY LINE ALUMINUM NITRIDE PIEZOELECTRIC LAYER,” the disclosuresof which are hereby incorporated by reference in its entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave elements.

Description of Related Technology

Acoustic wave devices such as delay lines and acoustic wave resonatorscan be implemented in radio frequency electronic systems. For instance,a radio frequency front end of a mobile phone can include one or moredelay lines and/or one or more acoustic wave filters that includes anacoustic wave resonator. A plurality of acoustic wave filters can bearranged as a multiplexer.

A delay line can include sets of interdigital transducer electrodes on apiezoelectric substrate. Example delay lines include Lamb wave delaylines and Rayleigh delay lines.

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters, bulk acoustic wave (BAW)filters, and Lamb wave filters. Example BAW resonators include film bulkacoustic wave resonators (FBARs) and solidly mounted resonators (SMRs).In BAW filters, acoustic waves propagate in a bulk of a piezoelectriclayer. A SAW filter can include an interdigital transductor electrode ona piezoelectric substrate and can generate a surface acoustic wave on asurface of the piezoelectric layer on which the interdigital transductorelectrode is disposed.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one aspect, an acoustic wave element is disclosed. The acoustic waveelement can include a piezoelectric layer that includes aluminumnitride. The acoustic wave element can also include a diamond likecarbon layer, and an interdigital transducer electrode positioned on thepiezoelectric layer. The piezoelectric layer can be positioned betweenthe interdigital transducer electrode and the diamond like carbon layer.The acoustic wave element can be configured to generate a Lamb wavehaving a wavelength of λ.

In an embodiment, the Lamb wave is a lowest-order antisymmetric modeLamb.

In an embodiment, the acoustic wave element further includes a supportlayer under the diamond like carbon layer. The support layer can be asilicon layer. The silicon layer can have a thickness that is greaterthan 200λ. The support layer can include at least one of silicondioxide, a ceramic, or sapphire.

In an embodiment, the piezoelectric layer is a doped aluminum nitridelayer. The piezoelectric layer can be doped with scandium.

In an embodiment, the interdigital transducer electrode is an aluminumelectrode.

In an embodiment, the piezoelectric layer is a thickness in a range from0.1λ to 1λ.

In an embodiment, the diamond like carbon layer has a thickness in arange from 2 The diamond like carbon layer can have the thickness in arange from 2λ to 10λ.

In an embodiment, the acoustic wave element is a Lamb wave resonator.

In an embodiment, the acoustic wave element is included in a Lamb wavedelay line.

In an embodiment, the acoustic wave element further includes a metallayer that is positioned between the piezoelectric layer and the diamondlike carbon layer. The metal layer can include titanium. The metal layercan further include molybdenum. The acoustic wave element can furtherinclude a support layer under the diamond like carbon layer. Theacoustic wave element can further include a silicon layer under thediamond like carbon layer.

In one aspect, an acoustic wave element configured to generate Lamb waveis disclosed. The acoustic wave element can include a piezoelectriclayer that includes aluminum nitride. The acoustic wave element can alsoinclude a high acoustic velocity layer positioned under thepiezoelectric layer. The high acoustic velocity layer has an acousticvelocity that is greater than an acoustic velocity of the piezoelectriclayer. The acoustic wave element can further include an interdigitaltransducer electrode positioned over the piezoelectric layer. Theacoustic wave element can be configured to generate a lowest-order antisymmetric mode Lamb wave that has a wavelength of λ.

In an embodiment, the acoustic wave element further includes a supportlayer positioned under the high acoustic velocity layer. The supportlayer can be a silicon layer. The silicon layer can have a thicknessthat is greater than 200λ.

In an embodiment, the piezoelectric layer is a doped aluminum nitridelayer. The piezoelectric layer can be doped with scandium.

In an embodiment, the high acoustic velocity layer is a diamond likecarbon layer.

In an embodiment, the high acoustic velocity layer is a diamond layer.

In an embodiment, the interdigital transducer electrode is an aluminumelectrode.

In an embodiment, the acoustic wave element further includes a supportlayer that includes at least one of silicon dioxide, a ceramic, orsapphire.

In an embodiment, the piezoelectric layer has a thickness in a rangefrom 0.1λ to 1λ.

In an embodiment, the high acoustic velocity layer has a thickness in arange from 2λ to 200λ. The high acoustic velocity layer can have thethickness in a range from 2λ to 50λ. The high acoustic velocity layercan have the thickness in a range from 2λ to 10λ.

In an embodiment, the acoustic wave element is a Lamb wave resonator.

In an embodiment, the acoustic wave element is included in a Lamb wavedelay line.

In an embodiment, the acoustic wave element further includes a metallayer positioned between the piezoelectric layer and the diamond likecarbon layer. The metal layer can include titanium. The metal layer canfurther include molybdenum. The acoustic wave element can furtherinclude a support layer under the diamond like carbon layer. Theacoustic wave element can further include a silicon layer under thediamond like carbon layer.

In one aspect, an acoustic wave element that is configured to generateLamb wave is disclosed. The acoustic wave element can include apiezoelectric layer that has an acoustic velocity of at least 10,000meters per second. The acoustic wave element can also include a diamondlike carbon layer that is positioned under the piezoelectric layer. Theacoustic wave element can further include an interdigital transducerelectrode that is positioned over the piezoelectric layer. Theinterdigital transducer electrode is configured to generate a Lamb wavehaving a wavelength of λ.

In an embodiment, a delay line includes the acoustic wave element. Thedelay line can have an operating frequency in a range from 5 gigahertzto 12 gigahertz. The delay line can have an operating frequency in arange from 8 gigahertz to 12 gigahertz.

In an embodiments, an acoustic wave filter includes the acoustic waveelement.

In one aspect, a Lamb wave delay line is disclosed. The Lamb wave delayline can include an aluminum nitride piezoelectric layer, and a firstinterdigital transducer electrode that is positioned over the aluminumnitride piezoelectric layer. The first interdigital transducer electrodeis configured to generate a second harmonic lowest-order antisymmetricmode Lamb wave that has a wavelength of λ. The aluminum nitridepiezoelectric layer can have a thickness in a range from 0.1λ to 1λ. TheLamb wave delay line can also include a second interdigital transducerelectrode positioned over the aluminum nitride piezoelectric layer. Thesecond interdigital transducer electrode is coupled to the firstinterdigital transducer electrode. The first interdigital transducerelectrode and the second interdigital transducer electrode are includedin a delay line.

In an embodiment, the piezoelectric layer has a thickness in a rangefrom 0.1λ to 0.5λ. The first interdigital transducer electrode can havea thickness in a range from 0.01λ to 0.1λ.

In an embodiment, the first interdigital transducer electrode has anaperture length in a range from 40λ to 60λ.

In an embodiment, the aluminum nitride piezoelectric layer is a dopedaluminum nitride piezoelectric layer.

In an embodiment, the doped aluminum nitride piezoelectric layer isdoped with scandium.

In an embodiment, the Lamb wave delay line has an operating frequency ina range from 5 gigahertz to 12 gigahertz. The Lamb wave delay line canhave an operating frequency in a range from 8 gigahertz to 12 gigahertz.The Lamb wave delay line can have an operating frequency in a range from8 gigahertz to 10 gigahertz.

In an embodiment, the second interdigital transducer electrode isconfigured to generate a second harmonic lowest-order antisymmetric modeLamb wave.

In one aspect, a Lamb wave delay line is disclosed. The lamb wave delayline can include an aluminum nitride piezoelectric layer, and two setsof interdigital transducer electrodes over the aluminum nitridepiezoelectric layer. The sets of interdigital transducer electrodesincludes a first interdigital transducer electrode and a secondinterdigital transducer electrode. The first interdigital transducerelectrode is configured to generate a second harmonic lowest-orderantisymmetric mode Lamb wave having a wavelength of λ. The piezoelectriclayer has a thickness in a range from 0.1λ to 1λ. The first interdigitaltransducer electrode and the second interdigital transducer electrodeare included in a delay line. The delay line has an operating frequencyin a range from 5 gigahertz to 12 gigahertz.

In an embodiment, the piezoelectric layer has a thickness in a rangefrom 0.1λ to 0.5λ. The first interdigital transducer electrode has athickness in a range from 0.01λ to 0.1λ.

In an embodiment, the first interdigital transducer electrode has anaperture length in a range from 40λ to 60λ.

In an embodiment, the aluminum nitride piezoelectric layer is a dopedaluminum nitride piezoelectric layer. The doped aluminum nitridepiezoelectric layer can be doped with scandium.

In an embodiment, the delay line matches a delay of a supply voltage toa corresponding delay arising from a phase difference between a radiofrequency input signal processed by a carrier branch and a radiofrequency input signal processed by a peaking branch.

In an embodiment, the delay line has an operating frequency in a rangefrom 8 gigahertz to 12 gigahertz. The delay line can have an operatingfrequency in a range from 8 gigahertz to 10 gigahertz.

In one aspect, a method of operating the Lamb wave delay line describedherein. The method can include receiving, by the Lamb wave delay line, aradio frequency signal, and providing, by the Lamb wave delay line, adelay for the radio frequency signal.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1A illustrates a cross section of an acoustic wave elementaccording to an embodiment.

FIG. 1B illustrates a displacement profile of the acoustic wave elementof FIG. 1A.

FIG. 2A illustrates a cross section of an acoustic wave elementaccording to another embodiment.

FIG. 2B illustrates a displacement profile of the acoustic wave elementof FIG. 2A.

FIG. 3A illustrates simulated total displacement profile of the acousticwave element of FIG. 2A at a resonance condition.

FIG. 3B illustrates simulated electric potential of the acoustic waveelement of FIG. 2A at the resonance condition.

FIG. 3C illustrates simulated stress of the acoustic wave element ofFIG. 2A at the resonance condition.

FIG. 4A illustrates simulated admittance results for the acoustic waveelement of FIG. 1A and acoustic element of FIG. 2A having an aluminumnitride (AlN) piezoelectric layer thickness of 0.2λ.

FIG. 4B illustrates simulated admittance results for the acoustic waveelement of FIG. 1A and acoustic element of FIG. 2A having the AlNpiezoelectric layer thickness of 0.3λ.

FIG. 4C illustrates simulated admittance results for the acoustic waveelement of FIG. 1A and acoustic element of FIG. 2A having the AlNpiezoelectric layer thickness of 0.5λ.

FIG. 5 illustrates a cross section of an acoustic wave element accordingto another embodiment.

FIG. 6 is a graph showing simulation results of admittance of acousticwave elements according to various embodiments.

FIG. 7A illustrates simulated total displacement profile of the acousticwave element of FIG. 5 at a resonance condition.

FIG. 7B illustrates simulated electric potential of the acoustic waveelement of FIG. 5 at the resonance condition.

FIG. 7C illustrates simulated electrical filed direction of the acousticwave element of FIG. 5 at the resonance condition.

FIG. 8 illustrates a schematic top view of an acoustic wave delay linewith electrical connections thereof, according to one embodiment.

FIG. 9A is a schematic diagram of a transmit filter that includes anacoustic wave resonator according to an embodiment.

FIG. 9B is a schematic diagram of a receive filter that includes anacoustic wave resonator according to an embodiment.

FIG. 10A is a schematic diagram of a radio frequency module thatincludes a Lamb wave element according to an embodiment.

FIG. 10B is a schematic diagram of a radio frequency module thatincludes a delay line according to an embodiment.

FIG. 11 is a schematic diagram of a radio frequency module that includesfilters with Lamb wave resonators according to an embodiment.

FIG. 12 is a schematic block diagram of a module that includes anantenna switch and duplexers that include a Lamb wave resonatoraccording to an embodiment.

FIG. 13A is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers that include a Lambwave resonator according to an embodiment.

FIG. 13B is a schematic block diagram of a module that includes filters,a radio frequency switch, and a low noise amplifier according to anembodiment.

FIG. 14A is a schematic block diagram of a wireless communication devicethat includes a filter with a Lamb wave element in accordance with oneor more embodiments.

FIG. 14B is a schematic block diagram of another wireless communicationdevice that includes a Lamb wave element in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings, where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Acoustic wave elements can include acoustic wave resonators and acousticwave delayer lines. Example acoustic wave elements disclosed hereininclude Lamb wave delay lines and Lamb wave resonators. A Lamb wavedelay line can include two sets of interdigital transducers. A delayline can be used to provide a delay for a radio frequency (RF) signal.The delay line can provide phase rotation. Delay lines can beimplemented in a variety of radio frequency applications. For example,delay lines can be used in a loop circuit coupled to the acoustic wavefilter, in which the loop circuit is configured to generate ananti-phase signal to a target signal at a particular frequency. In someinstances, a delay line can be implemented to reduce phase spreading.

Acoustic wave filters can filter radio frequency (RF) signals in avariety of applications, such as in an RF front end of a mobile phone.An acoustic wave filter can include Lamb wave resonators. A Lamb waveresonator can generate a Lamb wave.

In general, high quality factor (Q), large effective electromechanicalcoupling coefficient (k²), high frequency ability, and spurious freeresponse can be significant aspects for acoustic wave elements to enablelow-loss filters, delay lines, stable oscillators, and sensitivesensors.

Aspects of this disclosure relate to an acoustic wave element thatprovides high frequency ability. Various embodiments disclosed hereincan provide high frequency ability for lowest-order antisymmetric modeLamb waves. Various embodiments disclosed herein can provide improvedstructural ruggedness for an acoustic wave element operable at arelatively high frequency, while maintaining a relatively high qualityfactor (Q) and a large effective electromechanical coupling coefficient(k²).

Embodiments of an acoustic wave element disclosed herein include apiezoelectric layer (e.g., an aluminum nitride (AlN) piezoelectriclayer), and an interdigital transducer (IDT) electrode over the AlNpiezoelectric layer. The acoustic wave element can also include adiamond like carbon (DLC) layer under the AlN piezoelectric layer, and asupport layer (e.g., silicon (Si) layer) under the DLC layer. Theacoustic wave element can further include a metal layer between the DLClayer and the AlN piezoelectric layer. In some applications, the IDTelectrode can generate a second harmonic lowest-order antisymmetric modeLamb wave having a wavelength of λ. A second harmonic lowest-orderantisymmetric mode Lamb wave can be a largest resonance mode in such adevice and/or have a relatively small dispersion under a substrate. Lambwave elements disclosed herein can have relatively high resonantfrequencies, such as resonant frequencies in a range from about 5gigahertz (GHz) to 10 GHz.

Embodiments of this disclosure relate to a Lamb wave delay line thatincludes an aluminum nitride piezoelectric layer and interdigitaltransducer electrodes. The Lamb wave delay line can generate a secondharmonic lowest-order antisymmetric mode Lamb wave having a wavelengthof λ. A second harmonic lowest-order antisymmetric mode Lamb wave can bea largest resonance mode in such a device. The aluminum nitridepiezoelectric layer can have a thickness in a range from 0.1λ to 1λ. Insome embodiments, the thickness of the aluminum nitride piezoelectriclayer can be less than 1 micron. The Lamb wave delay lines can have arelatively high operating frequency, such as an operating frequency in arange from 5 GHz to 10 GHz.

FIG. 1A illustrates a cross section of an acoustic wave element 1according to an embodiment. The acoustic wave element 1 includes analuminum nitride (AlN) piezoelectric layer 10 and an interdigitaltransducer (IDT) electrode 12 over the AlN piezoelectric layer 10. Theacoustic wave element 1 can be arranged to generate a second harmoniclowest-order antisymmetric mode Lamb wave having a wavelength. Thematerial of the AlN piezoelectric layer 10 and a thickness H1 of the AlNpiezoelectric layer 10 are technical features that contribute to theacoustic wave element 1 being arranged to generate such a Lamb wave. Insome embodiments, the AlN piezoelectric layer 10 can be formed by way ofdeposition. In some embodiments, the acoustic wave element 1 can includea cavity (e.g., an air cavity) below the AlN piezoelectric layer 10.

The AlN piezoelectric layer 10 can be replaced with any suitablepiezoelectric layer. For example, the AlN piezoelectric layer 10 can bereplaced with any suitable electromechanical exchange material. Thepiezoelectric layer can include any suitable material that has anacoustic velocity of 10,000 meters per second (m/s) or greater, forexample. In some embodiments, the AlN piezoelectric layer 10 can bedoped with, for example, scandium (Sc).

A thickness H1 of the AlN piezoelectric layer 10 can be selected basedon a wavelength λ or L of an acoustic wave generated by the acousticwave element 1. The IDT electrode 12 has a pitch that sets thewavelength λ or L of the acoustic wave element 1. The AlN piezoelectriclayer 10 can be sufficiently thick to avoid significant frequencyvariation. In some embodiments, the thickness H1 of the AlNpiezoelectric layer can be in a range from 0.1λ to 1λ. In someinstances, the thickness H1 can be in a range from 0.1λ to 0.5λ. Thethickness H1 of the AlN piezoelectric layer 10 can be determined basedat least in part on, for example, the mode of the operation frequency.For example, when the wavelength λ is 2 μm, the thickness H1 of the AlNpiezoelectric layer 10 can be in a range from 0.2 μm to 2 μm.

The IDT electrode 12 can include a bus bar and fingers that extend fromthe bus bar. The fingers of the IDT electrode 12 have an active region.The active region can a region between edge portions of the fingers andgap portions. This region can be referred to as an aperture. The IDTelectrode 12 can include any suitable number of fingers. For example, insome applications, the IDT electrode 12 can include about 50 fingers. Insome embodiments, the aperture of the IDT electrode can be in a rangefrom 40λ to 60λ, for example, about 50λ.

The IDT electrode 12 can include any suitable IDT electrode material. Insome embodiments, the IDT electrode 12 can include an aluminum (Al) IDTelectrode. The IDT electrode 12 illustrated in FIG. 1A is a single layerIDT. However, the IDT electrode 12 can include a plurality of metallayers in some instances. The IDT electrode 12 may include one or moreother metals, such as copper (Cu), Magnesium (Mg), tungsten (W),titanium (Ti), the like, or any suitable combination thereof. The IDTelectrode 12 may include alloys, such as AlMgCu, AlCu, etc.

The IDT electrode 12 has a thickness H2. In some embodiments, thethickness H2 of the IDT electrode 12 can be in a range from 0.01λ to0.1λ. For example, when the wavelength λ is 2 μm, the thickness H2 ofthe IDT electrode 12 can be in a range from 0.02 μm to 0.2 μm.

The illustrated acoustic wave element 1 is a Lamb wave element. The Lambwave element can be included in a delay line in some embodiments. A Lambwave delay line can include two sets of interdigital transducers. Adelay-line can be used, for example, to match a delay of a supplyvoltage to a corresponding delay arising from a phase difference betweenan RF input signal processed by a carrier branch and an RF input signalprocessed by the peaking branch.

In some applications, the IDT electrode 12 can be configured to generatea second harmonic Lamb wave having a wavelength of λ. The secondharmonic Lamb wave can be a lowest-order antisymmetric mode Lamb wave.In some embodiments, the acoustic wave element 1 can be included in anultra-high frequency delay line. An operating frequency of theultra-high frequency delay line can be in a range from 3 GHz to 20 GHzin certain applications. For example, the operating frequency can be ina range from 5 GHz to 12 GHz. As another example, the operatingfrequency can be in a range from 8 GHz to 10 GHz. In certainapplications, the operating frequency of a delay line that include theLamb wave element 1 is about 8.5 GHz. Using the lowest orderantisymmetric Lamb wave mode can be beneficial in certain embodiments.The use of the lowest order antisymmetric Lamb wave mode can allow forhigher frequency operation than other modes.

FIG. 1B illustrates a displacement profile of the acoustic wave element1 of FIG. 1A. The dashed lines between FIGS. 1A and 1B show relativepositions of the AlN piezoelectric layer 10. FIG. 1B indicates thatlarger displacement is concentrated between the fingers of the IDTelectrode 12 and a smaller displacement below the fingers of IDTelectrode 12.

FIG. 2A illustrates a cross section of an acoustic wave element 2according to another embodiment. The acoustic wave element 2 includes analuminum nitride (AlN) piezoelectric layer 10 and an interdigitaltransducer (IDT) electrode 12 for removing cavity over the AlNpiezoelectric layer 10. The acoustic wave element 2 also includes adiamond like carbon (DLC) layer 14 under the AlN piezoelectric layer 10,and a silicon (Si) layer 16 under the DLC layer 14. The AlNpiezoelectric layer 10 and the IDT electrode 12 illustrated in FIG. 2Acan be generally similar or the same as the AlN piezoelectric layer 10and the IDT electrode 12, respectively, illustrated in FIG. 1A incertain embodiments.

In the acoustic wave element 2, the AlN piezoelectric layer 10 can bereplaced with any suitable piezoelectric layer. For example, thepiezoelectric layer can include any suitable material that has anacoustic velocity of 10,000 m/s or greater. In some embodiments, the AlNpiezoelectric layer 10 can be doped with, for example, scandium (Sc).

A thickness H1 of the AlN piezoelectric layer 10 can be selected basedon a wavelength λ or L of an acoustic wave generated by the acousticwave element 2. The IDT electrode 12 has a pitch that sets thewavelength λ or L of the acoustic wave element 2. The AlN piezoelectriclayer 10 can be sufficiently thick to avoid significant frequencyvariation. In some embodiments, the thickness H1 of the AlNpiezoelectric layer 10 can be in a range from 0.1λ to 1λ. In someinstances, the thickness H1 can be in a range from 0.1λ to 0.5λ. Thethickness H1 of the AlN piezoelectric layer 10 can be determined basedat least in part on, for example, the mode of the operation frequency.For example, when the wavelength λ is 2 μm, the thickness H1 of the AlNpiezoelectric layer 10 can be in a range from 0.2 μm to 2 μm.

The IDT electrode 12 can include a bus bar and fingers that extend fromthe bus bar. The fingers of the IDT electrode 12 have an active region.The active region can a region between edge portions of the fingers andgap portions. This region can be referred to as an aperture. The IDTelectrode 12 can include any suitable number of fingers. For example, insome applications, the IDT electrode 12 can include about 50 fingers. Insome embodiments, the aperture of the IDT electrode can be in a rangefrom 40λ to 60λ, for example, about 50λ.

The IDT electrode 12 can include any suitable IDT electrode material. Insome embodiments, the IDT electrode 12 can include an aluminum (Al) IDTelectrode. The IDT electrode 12 illustrated in FIG. 1A is a single layerIDT. However, the IDT electrodes 12 can include a plurality of metallayers in some instances. The IDT electrode 12 may include one or moreother metals, such as copper (Cu), Magnesium (Mg), tungsten (W),titanium (Ti), the like, or any suitable combination thereof. The IDTelectrode 12 may include alloys, such as AlMgCu, AlCu, etc.

The IDT electrode 12 has a thickness H2. In some embodiments, thethickness H2 of the IDT electrode 12 can be in a range from 0.01λ to0.1λ. For example, when the wavelength λ is 2 μm, the thickness H2 ofthe IDT electrode 12 can be in a range from 0.02 μm to 0.2 μm.

By having a relatively high acoustic velocity material for the DLC layer14, the DLC layer 14 can trap acoustic energy in the AlN piezoelectriclayer 10, such that the quality factor (Q) can be generally maintainedor unchanged as compared to an acoustic wave element without the DLClayer 14. The DLC layer 14 can be replaced with any other suitable highacoustic velocity layer. For example, the high acoustic velocity layercan include any material that has an acoustic velocity that is higherthan an acoustic velocity of a piezoelectric layer (e.g., the AlNpiezoelectric layer 10). In some embodiments, the high acoustic velocitylayer can include any material that has an acoustic velocity greaterthan 10,000 m/s.

The DLC layer has a thickness H3. In some embodiments, the thickness H3of the DLC layer 14 can be greater than about 2λ. For example, thethickness H3 of the DLC layer 14 can be in a range from 2λ to 200λ. Insome applications, the thickness H3 of the DLC layer 14 can bedetermined based, at least in part, on, for example, the mode of theoperation frequency. In some applications, the DLC layer 14 that has thethickness H3 equal to or greater than 2λ can have lower loss than theDLC layer 14 that has the thickness less than 2λ. In some applications,the DLC layer 14 can suppress an acoustic wave propagation in the Silayer 16. This may allow the acoustic wave element 2 to maintain highvelocity, high frequency operation with improved mechanical ruggednessas compared to an acoustic wave element without the DLC layer 14.

The Si layer 16 can be replaced with any suitable support layer. In someembodiments, the support layer can include a relatively high thermalconductivity material. For example, the support layer can include aceramic, silicon dioxide (SiO₂), sapphire, etc.

The Si layer 16 has a thickness H4. The thickness H4 of the Si layer 16can be, for example, greater than 200λ. In some embodiments, thethickness H4 of the Si layer 16 can be determined based at least in parton a desired final thickness of the acoustic wave element 2.

The DLC layer 14 and the Si layer 16 can individually or in combinationprovide mechanical support for the AlN piezoelectric layer 10. In someembodiments, the Si layer 16 may be omitted and only the DLC layer 14may provide support for the AlN piezoelectric layer 10. For example, alowest order antisymmetric mode Lamb wave velocity of the acoustic waveelement 2 can be about 10% higher than a similar acoustic wave elementthat does not include the DLC layer 14.

The acoustic wave element 2 can be an acoustic wave resonator or anacoustic wave delay line. In some applications, the acoustic waveresonator can be included in an acoustic wave filer. In someembodiments, the acoustic wave element 2 can be a Lamb wave element. TheLamb wave element can be a Lamb wave resonator in certain instances. ALamb wave resonator is a type of acoustic wave resonator. The Lamb waveelement can be a delay line in some instances. A Lamb wave delay linecan include two sets of interdigital transducers. A delay-line can beused, for example, to match a delay of a supply voltage to acorresponding delay arising from a phase difference between an RF inputsignal processed by a carrier branch and an RF input signal processed bythe peaking branch.

In some applications, the IDT electrode 12 can be configured to generatea second harmonic Lamb wave having a wavelength of λ. The secondharmonic Lamb wave can be a lowest-order antisymmetric mode Lamb wave.In some embodiments, the acoustic wave element 2 can include anultra-high frequency delay line. An operation frequency of theultra-high frequency delay line can be in a range from 3 GHz to 20 GHzin certain applications. For example, the operating frequency can be ina range from 5 GHz to 10 GHz. As another example, the operatingfrequency can be in a range from 8 GHz to 10 GHz. In certainapplications, the operating frequency of a delay line that includes theLamb wave element 1 is about 8.5 GHz. Using the lowest orderantisymmetric mode Lamb wave can be beneficial in certain embodiments.The use of the lowest order antisymmetric mode Lamb wave can allow forhigher frequency operation than other modes.

FIG. 2B illustrates a displacement profile of the acoustic wave element2 of FIG. 2A. The dashed lines between FIGS. 2A and 2B show relativepositions of the components of the acoustic wave element 2. As with FIG.1B, FIG. 2B indicates that larger displacement is concentrated betweenthe fingers of the IDT electrode 12 and a smaller displacement below thefingers of the IDT electrode 12. FIG. 2B also shows that thedisplacement propagates through at least a portion of the DLC layer 14.

FIGS. 3A to 3C illustrate simulated total displacement profile, electricpotential, and stress of the acoustic wave element 2 at a resonancecondition. The simulations are based on a lowest-order antisymmetricmode Lamb wave. The acoustic wave element 2 used for the simulationincludes an aluminum nitride (AlN) piezoelectric layer 10 with athickness H1 of 0.3λ, an IDT electrode 12 formed of an aluminum (Al) IDTelectrode with a thickness H2 of 0.03λ, a diamond like carbon (DLC)layer 14 with a thickness H3 of 2λ, and a silicon (Si) layer 16 with athickness H4 of 5λ.

FIG. 3A shows that the total displacement is distributed in the AlNpiezoelectric layer 10 and at an upper portion (near a boundary betweenthe AlN piezoelectric layer 10 and the DLC layer 14) of the DLC layer14. The total displacement is propagated through about 1λ of the DLClayer 14 from the boundary between the AlN piezoelectric layer 10 andthe DLC layer 14. At a lower portion of the DLC layer 14 opposite theupper portion, there is no notable displacement. Therefore, there is noor almost no displacement in the Si layer 16.

FIG. 3B shows that the electrical potential is concentrated at or nearthe boundary between the AlN piezoelectric layer 10 and the DLC layer14. High reflection can be assumed neat the boundary in such calculationresults. FIG. 3C shows that stress is propagated in the AlNpiezoelectric layer 10 and at the upper portion (near the boundarybetween the AlN piezoelectric layer 10 and the DLC layer 14) of the DLClayer 14.

FIGS. 4A to 4C illustrate simulated admittance results for the acousticwave element 1 and acoustic element 2 having various thicknesses H1(H1=0.2λ, 0.3λ, and 0.5λ) of the AlN piezoelectric layer 10. The y-axesof FIGS. 4A to 4C show the simulated admittance in decibel (dB) and thex-axes of FIGS. 4A-4C show the frequency in megahertz (MHz). Thesimulation is based on a lowest-order antisymmetric mode Lamb wave.

FIG. 4A shows the simulated result (1) for the acoustic wave element 1and the simulated result (2) for the acoustic wave element 2, when thethickness H1 of the AlN piezoelectric layer 10 is 0.2λ. The acousticvelocity of the acoustic element 2 increased about 16% relative to theacoustic velocity of the acoustic element 1. The coupling factor (K²)and the quality factor (Q) of the acoustic velocity of the acousticelement 2 are observed to be generally similar to the coupling factor(K²) and the quality factor (Q) of the acoustic velocity of the acousticelement 1.

FIG. 4B shows the simulated result (1) for the acoustic wave element 1and the simulated result (2) for the acoustic wave element 2, when thethickness H1 of the AlN piezoelectric layer 10 is 0.3λ. The acousticvelocity of the acoustic element 2 increased about 5% relative to theacoustic velocity of the acoustic element 1. The coupling factor (K²)and the quality factor (Q) of the acoustic velocity of the acousticelement 2 are observed to be generally similar to the coupling factor(K²) and the quality factor (Q) of the acoustic velocity of the acousticelement 1.

FIG. 4C shows the simulated result (1) for the acoustic wave element 1and the simulated result (2) for the acoustic wave element 2, when thethickness H1 of the AlN piezoelectric layer 10 is 0.5λ. The acousticvelocity of the acoustic element 2 increased about 8% relative to theacoustic velocity of the acoustic element 1. The coupling factor (K²)and the quality factor (Q) of the acoustic velocity of the acousticelement 2 are observed to be generally similar to the coupling factor(K²) and the quality factor (Q) of the acoustic velocity of the acousticelement 1.

FIG. 5 illustrates a cross section of an acoustic wave element 3according to another embodiment. The acoustic wave element 3 includes analuminum nitride (AlN) piezoelectric layer 10, an interdigitaltransducer (IDT) electrode 12 over the AlN piezoelectric layer 10, adiamond like carbon (DLC) layer 14 under the AlN piezoelectric layer 10,a silicon (Si) layer 16 under the DLC layer 14, and a metal layer 18between the AlN piezoelectric layer 10 and the DLC layer 14. The AlNpiezoelectric layer 10, the IDT electrode 12, the DLC layer 14, and theSi layer 16 illustrated in FIG. 5 can each be generally similar or thesame as the AlN piezoelectric layer 10, the IDT electrode 12, the DLClayer 14, and the Si layer 16, respectively, disclosed herein withrespect to other embodiments. The acoustic wave element 3 with the DLClayer 14 may exclude a cavity that may be required for a similarconventional acoustic wave element that does not have a DLC layer.

As illustrated in FIG. 5, the metal layer 18 can include a plurality oflayers of different metals. For example, the metal layer 18 can includea titanium (Ti) layer 18 a on the DLC layer 14 and a molybdenum (Mo)layer 18 b between the Ti layer 18 a and the AlN piezoelectric layer 10.In some applications, the metal layer 18 can help increase the couplingfactor (K²) of the acoustic wave element 3, and/or improve the qualityfactor (Q) of the acoustic wave element 3. This can be due to the metallayer 18 trapping charge. The Ti layer 18 a can help increase thebonding strength between the metal layer 18 and the DLC layer 14. Themetal layer 18 can include any suitable metal or any material with arelatively low acoustic loss. For example, the metal layer 18 caninclude one or more of aluminum (Al), tungsten (W), gold (Au), silver(Ag), copper (Cu), iridium (Ir) and/or the like material. In someembodiments, the metal layer 18 may not affect acoustic performance ofthe acoustic wave element 3. For example, the metal layer 18 can onlyaffect electrical performance of the acoustic wave element 3.

The metal layer 18 has a thickness H5. The thickness H5 of the metallayer 18 can be less than 0.01λ. For example, the thickness H5 of themetal layer 18 can be in a range from 0.002λ to 0.01λ. For example, whenthe wavelength λ is 2 μm, the thickness H5 of the metal layer 18 can bein a range from 0.004 μm to 0.02 μm.

FIG. 6 is a graph showing simulation results of admittance of acousticwave elements according to various embodiments. The y-axis of FIG. 6 isfor the admittance and the x-axis is for the frequency. The simulationswere run for the acoustic wave element 1, the acoustic element 2, andthe acoustic element 3. The simulation results in FIG. 6 show that thethickness H5 of the metal layer 18 of the acoustic element 3 affects theacoustic velocity. Further, when the metal layer 18 has the thickness H5that is less than 0.01λ, the reduction in acoustic velocity isrelatively small. At the same time, the coupling factor (K²) is improvedrelative to those without the metal layer 18.

FIGS. 7A to 7C illustrate simulated total displacement profile, electricpotential, and electrical field direction of the acoustic wave element 3at an resonance condition. The simulations are based on a lowest-orderantisymmetric mode Lamb wave. The acoustic wave element 3 used for thesimulation includes an aluminum nitride (AlN) piezoelectric layer 10, anIDT electrode 12, a diamond like carbon (DLC) layer 14, a silicon (Si)layer (not illustrated), and a metal layer 18 between the AlNpiezoelectric layer 10 and the DLC layer 14.

FIG. 7A shows that the total displacement is distributed in the AlNpiezoelectric layer 10, the metal layer 18, and at an upper portion(near a boundary between metal layer 18 and the DLC layer 14) of the DLClayer 14. The total displacement is propagated through about 1λ of theDLC layer 14 from the boundary between the metal layer 18 and the DLClayer 10. At a lower portion of the DLC layer 14 opposite the upperportion, there is no notable displacement.

FIG. 7B shows that the metal layer 18 affects the electrical potentialdistribution. This can allow for an increased quality factor (Q) of theacoustic wave element 3 as compared to a similar acoustic wave elementwithout the metal layer 18. FIG. 7C shows that the electrical field isconcentrated near the metal layer 18.

FIG. 8 illustrates a schematic top view of an acoustic wave delay line 4with electrical connections thereof, according to one embodiment. Theacoustic wave delay line 4 includes an aluminum nitride (AlN)piezoelectric layer 10, and an interdigital transducer (IDT) electrode12 over the AlN piezoelectric layer 10. The acoustic wave delay line 4can include one or more acoustic wave elements in accordance with anysuitable principles and advantages disclosed herein. As illustrated inFIG. 8, the acoustic wave delay line 4 can include two sets 22 a and 22b of interdigital transducers that are longitudinally coupled to eachother. A first set 22 a of the two sets of interdigital transducers isspaced apart along a longitudinal direction from a second set 22 b ofthe two sets of interdigital transducers. The first set 22 a iselectrically connected to an input port and the second set 22 b iselectrically connected to an output port. The first set 22 a and thesecond set 22 b are both electrically coupled and be grounded. The delayline 4 can include acoustic wave elements 1 in certain embodiments. Thedelay line 4 can include acoustic wave elements 2 in some otherembodiments. The delay line 4 can have a relatively high operatingfrequency. The operating frequency of the delay line 4 can be in afrequency range from 3 GHz to 20 GHz in certain applications. Forexample, the operating frequency can be in a range from 5 GHz to 10 GHz.As another example, the operating frequency can be in a range from 8 GHzto 10 GHz. In certain applications, the operating frequency of a delayline 4 is about 8.5 GHz.

An acoustic path between the two sets 22 a and 22 b of interdigitaltransducers has a distance D. In some applications, such as in case of asingle mode propagation, a delay in the acoustic wave delay line 4 canbe calculated by dividing the distance D by the acoustic velocity. Insome embodiments, the delay line 4 can include additional interdigitaltransducers positioned over the AlN piezoelectric layer 10. For example,the delay line 4 can include another pair of interdigital transducersets coupled to the two sets 22 a and 22 b of interdigital transducers.

FIG. 9A is a schematic diagram of an example transmit filter 100 thatincludes acoustic wave resonators according to an embodiment. Thetransmit filter 100 can be a band pass filter. The illustrated transmitfilter 100 is arranged to filter a radio frequency signal received at atransmit port TX and provide a filtered output signal to an antenna portANT. Some or all of the acoustic wave resonators TS1 to TS7 and/or TP1to TP5 can be acoustic wave resonators in accordance with any suitableprinciples and advantages disclosed herein. For instance, one or more ofthe acoustic wave resonators of the transmit filter 100 can be anacoustic wave element 2 of FIG. 2A or an acoustic wave element 3 of FIG.5. Alternatively or additionally, one or more of the acoustic waveresonators of the transmit filter 100 can be any acoustic wave elementdisclosed herein. Any suitable number of series acoustic wave resonatorsand shunt acoustic wave resonators can be included in a transmit filter100.

FIG. 9B is a schematic diagram of a receive filter 105 that includesacoustic wave resonators according to an embodiment. The receive filter105 can be a band pass filter. The illustrated receive filter 105 isarranged to filter a radio frequency signal received at an antenna portANT and provide a filtered output signal to a receive port RX. Some orall of the acoustic wave resonators RS1 to RS8 and/or RP1 to RP6 can beacoustic wave resonators in accordance with any suitable principles andadvantages disclosed herein. For instance, one or more of the acousticwave resonators of the receive filter 105 can be a acoustic wave element2 of FIG. 2A or an acoustic wave element 3 of FIG. 5. Alternatively oradditionally, one or more of the acoustic wave resonators of the receivefilter 105 can be any acoustic wave resonator disclosed herein. Anysuitable number of series acoustic wave resonators and shunt acousticwave resonators can be included in a receive filter 105.

Acoustic wave elements disclosed herein can be implemented in delaylines arranged to delay a radio frequency signal for a fifth generation(5G) technology application. Acoustic wave elements disclosed herein canbe implemented in filters arranged to filter a radio frequency signalfor a 5G technology application. Acoustic wave elements disclosed hereincan operate at relatively high operating frequencies. Such acoustic waveelements can be used to delay and/or filter radio frequency signalshaving a frequency of at least 5 GHz that are within a 5G New Radio (NR)operating band within Frequency Range 1 (FR1). FR1 can include afrequency range from 410 megahertz (MHz) to 7.125 gigahertz (GHz), forexample, as specified in a current 5G NR specification. In certainimplementations, acoustic wave elements disclosed herein can delayand/or filter radio frequency signals having frequencies above FR1.According to various implementations, acoustic wave elements disclosedherein can delay and/or filter radio frequency signals havingfrequencies above 6 GHz, such as radio frequency signals in a frequencyrange from 6 GHz to 10 GHz.

FIG. 10A is a schematic diagram of a radio frequency module 175 thatincludes an acoustic wave component 176 according to an embodiment. Theillustrated radio frequency module 175 includes the acoustic wavecomponent 176 and other circuitry 177. The acoustic wave component 176can include one or more acoustic wave elements with any suitablecombination of features of the acoustic wave element disclosed herein.The acoustic wave component 176 can include an acoustic wave die thatincludes acoustic wave elements.

The acoustic wave component 176 shown in FIG. 10A can include acousticwave elements 178 and terminals 179A and 179B. The acoustic waveelements 178 can include one or more acoustic wave elements with anysuitable combination of features of the acoustic wave element disclosedherein. For example, one or more of the acoustic wave elements 178 canbe an acoustic wave resonator included in an acoustic wave filter andimplemented in accordance with any suitable principles and advantages ofthe acoustic wave element 2 of FIG. 2A and/or any acoustic waveresonators disclosed herein The acoustic wave elements 178 can implementone or more delay lines. Alternatively or additionally, the acousticwave elements 178 can be included in one or more acoustic wave filtersand/or implement one or more acoustic wave filters.

The terminals 179A and 179B can serve, for example, as an input contactand an output contact. The acoustic wave component 176 and the othercircuitry 177 are on a common packaging substrate 180 in FIG. 10A. Thepackage substrate 180 can be a laminate substrate. The terminals 179Aand 179B can be electrically connected to contacts 181A and 181B,respectively, on the packaging substrate 180 by way of electricalconnectors 182A and 182B, respectively. The electrical connectors 182Aand 182B can be bumps or wire bonds, for example. The other circuitry177 can include any suitable additional circuitry. For example, theother circuitry can include one or more one or more power amplifiers,one or more radio frequency switches, one or more additional filters,one or more low noise amplifiers, the like, or any suitable combinationthereof. The radio frequency module 175 can include one or morepackaging structures to, for example, provide protection and/orfacilitate easier handling of the radio frequency module 175. Such apackaging structure can include an overmold structure formed over thepackaging substrate 180. The overmold structure can encapsulate some orall of the components of the radio frequency module 175.

FIG. 10B is a schematic diagram of a radio frequency module 175′ thatincludes an acoustic wave component 176′ according to an embodiment. Theradio frequency module 175′ can be generally similar to the radiofrequency module 175 illustrated in FIG. 10A. The illustrated radiofrequency module 175′ includes the acoustic wave component 176′ andother circuitry 177. The acoustic wave component 176′ can include one ormore acoustic wave elements with any suitable combination of features ofthe acoustic wave element disclosed herein. The acoustic wave component176′ can include an acoustic wave die that includes acoustic waveelements. The acoustic wave component 176′ can include a delay line178′.

FIG. 11 is a schematic diagram of a radio frequency module 184 thatincludes an acoustic wave resonator according to an embodiment. Asillustrated, the radio frequency module 184 includes duplexers 185A to185N that include respective transmit filters 186A1 to 186N1 andrespective receive filters 186A2 to 186N2, a power amplifier 187, aselect switch 188, and an antenna switch 189. In some instances, themodule 184 can include one or more low noise amplifiers configured toreceive a signal from one or more receive filters of the receive filters186A2 to 186N2. The radio frequency module 184 can include a packagethat encloses the illustrated elements. The illustrated elements can bedisposed on a common packaging substrate 180. The packaging substratecan be a laminate substrate, for example.

The duplexers 185A to 185N can each include two acoustic wave filterscoupled to a common node. The two acoustic wave filters can be atransmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be band pass filters arranged tofilter a radio frequency signal. One or more of the transmit filters186A1 to 186N1 can include one or more acoustic wave resonators inaccordance with any suitable principles and advantages disclosed herein.Similarly, one or more of the receive filters 186A2 to 186N2 can includeone or more acoustic wave resonators in accordance with any suitableprinciples and advantages disclosed herein. Although FIG. 11 illustratesduplexers, any suitable principles and advantages disclosed herein canbe implemented in other multiplexers (e.g., quadplexers, hexaplexers,octoplexers, etc.) and/or in switch-plexers.

The power amplifier 187 can amplify a radio frequency signal. Theillustrated switch 188 is a multi-throw radio frequency switch. Theswitch 188 can electrically couple an output of the power amplifier 187to a selected transmit filter of the transmit filters 186A1 to 186N1. Insome instances, the switch 188 can electrically connect the output ofthe power amplifier 187 to more than one of the transmit filters 186A1to 186N1. The antenna switch 189 can selectively couple a signal fromone or more of the duplexers 185A to 185N to an antenna port ANT. Theduplexers 185A to 185N can be associated with different frequency bandsand/or different modes of operation (e.g., different power modes,different signaling modes, etc.).

FIG. 12 is a schematic block diagram of a module 190 that includesduplexers 191A to 191N and an antenna switch 192. One or more filters ofthe duplexers 191A to 191N can include any suitable number of acousticwave resonators in accordance with any suitable principles andadvantages discussed herein. Any suitable number of duplexers 191A to191N can be implemented. The antenna switch 192 can have a number ofthrows corresponding to the number of duplexers 191A to 191N. Theantenna switch 192 can electrically couple a selected duplexer to anantenna port of the module 190.

FIG. 13A is a schematic block diagram of a module 210 that includes apower amplifier 212, a radio frequency switch 214, and duplexers 191A to191N in accordance with one or more embodiments. The power amplifier 212can amplify a radio frequency signal. The radio frequency switch 214 canbe a multi-throw radio frequency switch. The radio frequency switch 214can electrically couple an output of the power amplifier 212 to aselected transmit filter of the duplexers 191A to 191N. One or morefilters of the duplexers 191A to 191N can include any suitable number ofacoustic wave resonators in accordance with any suitable principles andadvantages discussed herein. Any suitable number of duplexers 191A to191N can be implemented.

FIG. 13B is a schematic block diagram of a module 215 that includesfilters 216A to 216N, a radio frequency switch 217, and a low noiseamplifier 218 according to an embodiment. One or more filters of thefilters 216A to 216N can include any suitable number of acoustic waveresonators in accordance with any suitable principles and advantagesdisclosed herein. Any suitable number of filters 216A to 216N can beimplemented. The illustrated filters 216A to 216N are receive filters.In some embodiments (not illustrated), one or more of the filters 216Ato 216N can be included in a multiplexer that also includes a transmitfilter. The radio frequency switch 217 can be a multi-throw radiofrequency switch. The radio frequency switch 217 can electrically couplean output of a selected filter of filters 216A to 216N to the low noiseamplifier 218. In some embodiments (not illustrated), a plurality of lownoise amplifiers can be implemented. The module 215 can includediversity receive features in certain applications.

FIG. 14A is a schematic diagram of a wireless communication device 220that includes filters 223 in a radio frequency front end 222 accordingto an embodiment. The filters 223 can include one or more acoustic waveresonators in accordance with any suitable principles and advantagesdiscussed herein. The wireless communication device 220 can be anysuitable wireless communication device. For instance, a wirelesscommunication device 220 can be a mobile phone, such as a smart phone.As illustrated, the wireless communication device 220 includes anantenna 221, an RF front end 222, a transceiver 224, a processor 225, amemory 226, and a user interface 227. The antenna 221 cantransmit/receive RF signals provided by the RF front end 222. Such RFsignals can include carrier aggregation signals. Although notillustrated, the wireless communication device 220 can include amicrophone and a speaker in certain applications.

The RF front end 222 can include one or more delay lines, one or morepower amplifiers, one or more low noise amplifiers, one or more RFswitches, one or more receive filters, one or more transmit filters, oneor more duplex filters, one or more multiplexers, one or more frequencymultiplexing circuits, the like, or any suitable combination thereof.The RF front end 222 can transmit and receive RF signals associated withany suitable communication standards. The filters 223 can include one ormore acoustic wave resonators that includes any suitable combination offeatures discussed with reference to any embodiments discussed above.Alternatively or additionally, the RF front end 222 can include one ormore delay lines that include an acoustic wave element that includes anysuitable combination of features discussed with reference to anyembodiments discussed above.

The transceiver 224 can provide RF signals to the RF front end 222 foramplification and/or other processing. The transceiver 224 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 222. The transceiver 224 is in communication with the processor 225.The processor 225 can be a baseband processor. The processor 225 canprovide any suitable base band processing functions for the wirelesscommunication device 220. The memory 226 can be accessed by theprocessor 225. The memory 226 can store any suitable data for thewireless communication device 220. The user interface 227 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 14B is a schematic diagram of a wireless communication device 230that includes filters 223 in a radio frequency front end 222 and asecond filter 233 in a diversity receive module 232. The wirelesscommunication device 230 is like the wireless communication device 200of FIG. 14A, except that the wireless communication device 230 alsoincludes diversity receive features. As illustrated in FIG. 14B, thewireless communication device 230 includes a diversity antenna 231, adiversity module 232 configured to process signals received by thediversity antenna 231 and including filters 233, and a transceiver 234in communication with both the radio frequency front end 222 and thediversity receive module 232. The filters 233 can include one or moreacoustic wave resonators that include any suitable combination offeatures discussed with reference to any embodiments discussed above.Alternatively or additionally, the diversity receive module 232 caninclude one or more delay lines that include an acoustic wave elementthat includes any suitable combination of features discussed withreference to any embodiments discussed above. In certain instances, thediversity receive module 232 can be considered part of a RF front end.

Any of the embodiments described above can be implemented in mobiledevices such as cellular handsets. The principles and advantages of theembodiments can be used for any systems or apparatus, such as any uplinkcellular device, that could benefit from any of the embodimentsdescribed herein. The teachings herein are applicable to a variety ofsystems. Although this disclosure includes some example embodiments, theteachings described herein can be applied to a variety of structures.Any of the principles and advantages discussed herein can be implementedin association with RF circuits configured to process signals having afrequency in a range from about 30 kHz to 300 GHz, such as a frequencyin a range from about 450 MHz to 8.5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as die and/or acoustic wave filter assembliesand/or packaged radio frequency modules, uplink wireless communicationdevices, wireless communication infrastructure, electronic testequipment, etc. Examples of the electronic devices can include, but arenot limited to, a mobile phone such as a smart phone, a wearablecomputing device such as a smart watch or an ear piece, a telephone, atelevision, a computer monitor, a computer, a modem, a hand-heldcomputer, a laptop computer, a tablet computer, a personal digitalassistant (PDA), a microwave, a refrigerator, an automobile, a stereosystem, a DVD player, a CD player, a digital music player such as an MP3player, a radio, a camcorder, a camera, a digital camera, a portablememory chip, a washer, a dryer, a washer/dryer, a peripheral device, awrist watch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure.

What is claimed is:
 1. An acoustic wave element comprising: apiezoelectric layer including aluminum nitride; a diamond like carbonlayer; and an interdigital transducer electrode on the piezoelectriclayer, the piezoelectric layer being positioned between the interdigitaltransducer electrode and the diamond like carbon layer, the acousticwave element is configured to generate a Lamb wave having a wavelengthof λ.
 2. The acoustic wave element of claim 1 wherein the Lamb wave is alowest-order antisymmetric mode Lamb.
 3. The acoustic wave element ofclaim 1 further comprising a support layer under the diamond like carbonlayer.
 4. The acoustic wave element of claim 1 wherein the piezoelectriclayer is a doped aluminum nitride layer doped with scandium.
 5. Theacoustic wave element of claim 1 wherein the piezoelectric layer has athickness in a range from 0.1λ to 1λ.
 6. The acoustic wave element ofclaim 1 wherein the diamond like carbon layer has a thickness in a rangefrom 2λ to 200λ.
 7. The acoustic wave element of claim 1 is included ina Lamb wave delay line.
 8. The acoustic wave element of claim 1 furthercomprising a metal layer positioned between the piezoelectric layer andthe diamond like carbon layer.
 9. The acoustic wave element of claim 8wherein the metal layer includes titanium or molybdenum.
 10. Theacoustic wave element of claim 9 further comprising a support layerunder the diamond like carbon layer.
 11. An acoustic wave elementconfigured to generate Lamb wave, the acoustic wave element comprising:a piezoelectric layer including aluminum nitride; a high acousticvelocity layer under the piezoelectric layer, the high acoustic velocitylayer having an acoustic velocity that is greater than an acousticvelocity of the piezoelectric layer; and an interdigital transducerelectrode over the piezoelectric layer, the acoustic wave elementconfigured to generate a lowest-order antisymmetric mode Lamb wavehaving a wavelength of λ.
 12. The acoustic wave element of claim 11further comprising a support layer under the high acoustic velocitylayer, wherein the support layer is a silicon layer.
 13. The acousticwave element of claim 11 wherein the piezoelectric layer is a dopedaluminum nitride layer.
 14. The acoustic wave element of claim 11wherein the high acoustic velocity layer is a diamond like carbon layer.15. The acoustic wave element of claim 11 wherein the piezoelectriclayer has a thickness in a range from 0.1λ to 1λ.
 16. The acoustic waveelement of claim 11 wherein the high acoustic velocity layer has athickness in a range from 2λ to 200λ.
 17. The acoustic wave element ofclaim 11 is included in a Lamb wave delay line.
 18. The acoustic waveelement of claim 11 further comprising a metal layer positioned betweenthe piezoelectric layer and the diamond like carbon layer.
 19. Anacoustic wave element configured to generate Lamb wave, the acousticwave element comprising: a piezoelectric layer having an acousticvelocity of at least 10,000 meters per second; a diamond like carbonlayer under the piezoelectric layer; and an interdigital transducerelectrode over the piezoelectric layer, the interdigital transducerelectrode is configured to generate a Lamb wave having a wavelength ofλ.
 20. A delay line comprising the acoustic wave element of claim 19wherein the delay line has an operating frequency in a range from 5gigahertz to 12 gigahertz.